The present disclosure relates to a diode and a method of manufacturing a diode. In particular, the present disclosure relates to a diode of a configuration in which electrodes are provided on both surfaces of a semiconductor layer which is configured using a compound semiconductor and a method of manufacturing the diode.
Gallium nitride (GaN), which is a compound semiconductor with a wide band gap, from the perspective of the physical properties thereof, is being focused on not only as a semiconductor material for optical devices, but also for power devices such as power supplies and inverters. This is because, in comparison with existing power devices which use silicon (Si), it is possible to realize a device of higher efficiency and higher performance.
In the manufacturing of such a power device system diode, generally, a gallium nitride layer is used which is epitaxially grown on a supporting substrate formed from different types of single crystal material such as silicon carbide (SiC), sapphire (Al2O3) and silicon (Si). In this case, a method of epitaxially growing a gallium nitride layer in a lateral direction in relation to a supporting substrate (epitaxial lateral overgrowth: ELO) is adopted as a method for obtaining a gallium nitride layer of favorable crystalline properties.
However, in a gallium nitride layer obtained using such epitaxial growth, a region containing a higher density of crystal defects than the other portions is generated as a threading dislocation region which penetrates the layer. Therefore, in a vertical device provided with electrodes in a state of interposing the layer, when such a threading dislocation region encroaches on the junction surface between the layer and the electrode, an ideal junction is not formed in the region and there is a concern that this will result in the occurrence of a leak current.
Therefore, a configuration is disclosed in which, in a gallium nitride layer obtained using epitaxial growth, a groove is formed in the region of a high threading dislocation density, a silicon nitride film is formed within the groove using patterning, and an electrode is formed to bridge over the silicon nitride film. According to this configuration, it is possible to reduce the influence of the threading dislocation while increasing the device surface area (refer to Japanese Unexamined Patent Application Publication No. 2007-184371 and Japanese Unexamined Patent Application Publication No. 2008-130927).